This invention generally relates to structural condition monitoring. More particularly, this invention relates to monitoring the condition of components within a helicopter rotor assembly.
It has become increasingly desirable to monitor the structural condition of helicopter rotor components. Early detection of potential failures or fractures within the structural components provides the ability to perform preventative maintenance and avoid potential component failure.
One challenge associated with monitoring such components is the large amount of vibration that is normally associated with the components during helicopter operation. Such vibratory influences have traditionally presented noise that interfered with the ability to adequately detect any structural flaws.
More recent advances include the development of piezoelectric sensors that are capable of detecting stress energy within a component. An example of such sensors is shown in U.S. Pat. No. 4,071,658.
While such sensors have become available, their usefulness within certain applications has not been exploited. There is a need for appropriately treating a signal from such a sensor in order to derive useful information for a given situation.
This invention provides an acoustic emission-based system for monitoring the structural condition of a component within a helicopter rotor assembly.
In general terms, this invention is a system for determining a structural condition of a portion of a helicopter rotor assembly. The inventive system includes a piezoelectric sensor that can be supported on a portion of the rotor assembly. The sensor provides a signal indicative of stress waves in at least one portion of the rotor assembly. A signal processor processes the sensor signal and provides an output signal having at least one characteristic that is indicative of the content of the sensor signal. A signal analyzer receives the output signal and determines the structural condition based upon the output signal characteristic.
In the preferred embodiment, the signal processor includes a demodulator portion that demodulates the sensor signal to thereby generate an envelope representation of the sensor signal. The envelope representation is more readily transmitted to the signal analyzer and handled in a more efficient manner. The demodulated envelope signal, therefore, provides the necessary structural information without the complexity of the original sensor signal.
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows.